65 Fuelie - 11:1 compression - Octane Booster?

[Brooks R.]

I am about to rebuild my fuelie to orginal specs with the 30-30 cam and 11:1 compression.

I hear three schools of thought.

1) This is ok if timing is correct, RPMs kept high, and 91 Octane pump gas

2) Don't do it, run no more than 10:1 compression

3) Ok to go 11:1 but use Octane booster or go to my local airport for 100LL aviation gas.

Looking for others who have taken one or more of these paths and still have a running engine.

Thanks

[Peter J.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

11 to 1 .30 over forged pistons in 66 L-79 and I have had no problems with detonation on premium (92/93 octane). Just a side note on the rebuild, my builder like many builds a lot of race engines and is quite experienced advice me not to use hardened valve seats as my heads didn't need them. I thought he was wrong and insisted but after reading posts on this board by some of the more experienced engine guys looks like my builder knew what he was talking about on this subject too.

[Joe R.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

I am about to rebuild my fuelie to orginal specs with the 30-30 cam and 11:1 compression.

I hear three schools of thought.

1) This is ok if timing is correct, RPMs kept high, and 91 Octane pump gas

2) Don't do it, run no more than 10:1 compression

3) Ok to go 11:1 but use Octane booster or go to my local airport for 100LL aviation gas.

Looking for others who have taken one or more of these paths and still have a running engine.

Thanks

Brooks,

Does it detonate right now? What octane gas are you using? If it doesn't detonate right now on say 91 octane gas, you should be able to rebuild it using the same compression ratio (CR) you have now without any trouble. I've seen Duke post on here many times that the CR that Chevy advertised was usually about 0.5 higher than actual. I can't remember if he recommends 10:1 or 10.5:1 for small blocks. He had an article in the Restorer in fairly recent times about managing compression ratio. Do the measurements and the math prior to and during the rebuild. The easiest way to hit the number you need is by choosing the thickness of the head gasket. Don't let the machine shop deck the block, especially on the passenger side, that will mess up the stamp pad - numbers and broach marks. Of course, I'm assuming that you have an original, untouched engine. I would recommend avoiding octane boosters, I hear most of them are snake oil anyway.

Joe

[Clem Z.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

if you are not going to deck the block and the heads have not been cut you will not be at 11:1 CR. make sure the engine builder removes all sharp edges from the pistons and combustion chambers in the heads.

[George J.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

I rebuilt my '65 fuelie about 9 years ago. Used the Federal Mogul 30-30 cam, stock replacement type pistons which gave an actual measured CR of 10.2 or 10.3 to 1. I set the timing at 38 degrees total and have never had any detonation or problems with premium pump gas. In Detroit it is 93 octane with 10% ethanol. No problems other than the need to feather the throttle after a hot start, and driving away as soon as starting helps. Everything else is stock except ARP rod bolts and roller tip rocker arms. Oh, and I don't use the dated wires or the shielding and it idles at 1200rpms.

[Duke W.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

The quality of the final product will be directly proportional to how much research and planning you do on the front end.

Get the Corvette Restorer CD and read the circa 2008 article on managing CR. Also research this forum searching "327 LT-1" for all the research and dyno testing that was done on this configuration including following the links to the Corvette Forum with all the dyno test data.

Don't forget your OE connecting rods a junk, and a set of Eagle SIR 5700P are only about 250 bucks.

You don't have to reinvent the wheel. Restoring a SHP/FI small block, using all OE equivalent replacement parts (with the exception of the rods and some other minor items depending on the OE configuration) that has decent low end torque (I consider 80 percent of peak at 2000 to be the minimum for an acceptably performing road engine.) and makes useable power to 7200 with OE relilablility and close to 300 SAE corrected RWHP without affecting visual appearance or idle behavior has been system engineered, built, proven with testing, and documented.

Duke

[James G.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

Hi BROOKS,

I have a 65 FUEL INJECTION SURVEY that was started in 1977. DREW PAPSUN, and I merged our two SURVEYS back in 2004. Many 65 fuel injection experts have kept this service alive. IS YOUR CAR INCLUDED? I would be happy to send you info and add you to the list. We now have 545 of the 711 cars made accounted for.

[Brooks R.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

Thanks Duke,

I purchased the CD and review the information there and from the archives.

The quality of the final product will be directly proportional to how much research and planning you do on the front end.

Get the Corvette Restorer CD and read the circa 2008 article on managing CR. Also research this forum searching "327 LT-1" for all the research and dyno testing that was done on this configuration including following the links to the Corvette Forum with all the dyno test data.

Don't forget your OE connecting rods a junk, and a set of Eagle SIR 5700P are only about 250 bucks.

You don't have to reinvent the wheel. Restoring a SHP/FI small block, using all OE equivalent replacement parts (with the exception of the rods and some other minor items depending on the OE configuration) that has decent low end torque (I consider 80 percent of peak at 2000 to be the minimum for an acceptably performing road engine.) and makes useable power to 7200 with OE relilablility and close to 300 SAE corrected RWHP without affecting visual appearance or idle behavior has been system engineered, built, proven with testing, and documented.

Duke

[Brooks R.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

Hi Clem,

The heads will be ported, polished, and port matched with new valves and springs. The block has been decked and I don't yet know if the heads need surfacing.

My goal for the motor is to be able to get as much horsepower as possible from original design parts, but be able to drive 3 to 4 thousand miles a year on pump gas without using additive.

I realize this is a situation of compromise, just not sure how far to go.

Thanks

if you are not going to deck the block and the heads have not been cut you will not be at 11:1 CR. make sure the engine builder removes all sharp edges from the pistons and combustion chambers in the heads.

[Joe R.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

Hi Clem,

The heads will be ported, polished, and port matched with new valves and springs. The block has been decked and I don't yet know if the heads need surfacing.

Thanks

Brooks,

Polishing the heads is counter-productive as far a horsepower goes.

Joe

[Duke W.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

"Polishing" is not a good idea for a road engine, especially if carbureted. The reasons are outlined in "The Tale of Two Camshafts" article in the Fall 2010 Corvette Restorer.

It might help a port injected engine, but I doubt if the benefits are worth the cost on a road engine.

Best broad range performance on a road engine is accomplished by what I call "head massaging", which basically consists of pocket porting, port matching, and a muli-angle valve job.

The benefits are about the same on any vintage Corvette engine regardless of original power rating - 7-10 percent more top end power with 500-1000 more useable revs at the top end and 3-5 percent more peak torque with no significant loss of low end torque, so you get to have your cake and eat it to.

Head massaging is the most effective way to get "more power" (and revs) on any vintage engine application using all the original components, so its idle and normal driving behavior are retained, but the engine will be much stronger in the upper half of the rev range with more useable revs to boot.

Duke

[Michael H.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

"Polishing" is not a good idea for a road engine, especially if carbureted.
Duke

I agree with Duke. (WHAT!) I don't think enlargine or polishing the intake ports is a positive move for a street engine. Smaller is better for low to mid range operation. (up to 6500-7000 RPM)
It may help at 7000 RPM and above but it hurts the mid range.
Velocity is the secret. Not continuous mass air flow.

[Duke W.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

As I explained in the "Tale of Two Camshafts" article, the purpose of "head massaging" on road engines is to improve the port flow coefficient without increasing port area to any significant degree.

This provides the improvement in top end power and rev range without affecting low end torque.

Polishing is not adviseable on carbureted road engines because port surface roughness helps breaks up the laminar boundary layer along the port walls, which helps keep the liquid fuel droplets in suspension and evaporating in the air stream rather than clinging to the port walls.

Duke

[Brooks R.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

Thanks Duke and Michael

I will amend my request for machining the heads to only "massage" the heads.

I will also read your article Duke on the "Tale of Two Camshafts".

As I explained in the "Tale of Two Camshafts" article, the purpose of "head massaging" on road engines is to improve the port flow coefficient without increasing port area to any significant degree.

This provides the improvement in top end power and rev range without affecting low end torque.

Polishing is not adviseable on carbureted road engines because port surface roughness helps breaks up the laminar boundary layer along the port walls, which helps keep the liquid fuel droplets in suspension and evaporating in the air stream rather than clinging to the port walls.

Duke

[Scott M.]

Re: 65 Fuelie - 11:1 compression - Octane Booster?

I don't see an answer to the OPs original question, will a true 11:1 327 w/ 30-30 run well on crappy 91 octane. I know one of Duke's LT1 327s runs very well at 10.5:1 which the owner feels is the maximum compression ratio for pump gas.